Thousands of Canadians are asking American regulators not to allow oil drilling in an Alaskan wildlife sanctuary that is home to a crucial transboundary caribou herd.

The request comes in a letter delivered Tuesday, the last day for comments to the U.S. Bureau of Land Management on its plans for an environmental assessment for energy exploration in the Alaskan National Wildlife Refuge, calving grounds for the Porcupine caribou herd.

“Oil and gas extraction has no place in the Arctic refuge,” says the letter, which was organized by several Canadian environmental groups.

More than 14,000 Canadians have signed it. Their voices join more than a half million Americans who have also written the agency to oppose the drilling program.

“We have a stake in this,” said Dana Tizya-Tramm, a councillor for Yukon’s Gwich’In First Nation, which depends on the herd. “These are transboundary animals.”

The governments of Canada, Yukon and Northwest Territories, as well as several First Nations, met in Inuvik, N.W.T., last December to discuss fears the refuge would be opened. They all signed an agreement promising to fight to uphold the treaty.

Despite those promises, none of the governments was immediately able to say if it had made a submission to the bureau.

The animals are protected under a U.S.-Canada treaty, which commits both nations to preserve them. The herd calves in Alaska, but its 218,000 caribou spend most of their time in Canada.

The herd is the largest and healthiest in the North and one that is considered crucial to the physical and cultural health of the Gwich’In people in Canada’s northwest.

Tizya-Tramm said the Gwich’In have been lobbying hard against drilling. He was just back from Washington, D.C., where he spoke with U.S. lawmakers.

He said political support for industry in the United States is damaging the credibility of the assessment. Tizya-Tramm said the one year allotted for a review is far short of what’s required.

“This is an extremely sensitive area,” he said. “It goes to show where their real mandate is. This process doesn’t really have any integrity.”

A request to hold one of the public hearings in Canada before the actual environmental assessment was denied.

Canadian environmental groups have also intervened. Nature Canada and the Canadian Parks and Wilderness Society have both made submissions to the land management bureau.

Although the Porcupine herd spends most of its time in Canada, the herd calves along the Alaska coast because the region is sheltered from predators while offering a rich diet of grasses and sedges. Winds off the Beaufort Sea reduce the clouds of biting insects.

It’s the last five per cent of the Alaskan coast that has remained closed to exploration. Although caribou and energy development co-exist elsewhere in the state, studies suggest that caribou don’t tolerate development on their calving grounds.

Several studies have concluded that caribou cows are highly sensitive to disturbance during the weeks before and after birth.